WASHINGTON — North Korea confirmed on Tuesday that it had conducted its third, long-threatened nuclear test, according to the official KCNA news service, posing a new challenge for the Obama administration in its effort to keep the country from becoming a full-fledged nuclear power.
The KCNA said it used a “miniaturized and lighter nuclear device with greater explosive force than previously” and that the test “did not pose any negative impact on the surrounding ecological environment.”
Many nations initially detected the test as seismic activity centered near the same location where the North conducted tests in 2006 and 2009. The United States Geological Survey said it was only a kilometer underground, an indication consistent with a nuclear blast. And in Vienna, the organization that monitors the Comprehensive Nuclear Test Ban Treaty said that tremor had “clear explosionlike characteristics.”
Preliminary estimates suggested a test far larger than the previous two conducted by the North, though probably less powerful than the first bomb the United States dropped on Japan, in Hiroshima, in 1945.
The test is the first under the country’s new leader, Kim Jong Un, and an open act of defiance to the Chinese, who urged the young leader not to risk open confrontation by setting off the weapon. Just in the past few days a Chinese newspaper that is often reflective of the government’s thinking said the North must ‘‘pay a heavy price’’ if it proceeded with the test.
The United Nations secretary-general Ban Ki-moon, condemned the test in a statement Tuesday.
Past UN Security Council sanctions have not deterred the country from accelerating its missile and nuclear programs. And recent actions, including a successful missile test nearly two months ago that reached as far as the Philippines and sent a washing machine-sized satellite into space, have dashed hopes that the country’s Swiss-educated new leader might be willing to focus on economic reform rather than pursuing the path taken by his father and grandfather: open defiance of the country’s adversaries.
The Obama administration has already threatened to take additional action to penalize the North if it conducts a test, through the United Nations. But there are few sanctions left to apply against the most unpredictable country in Asia. The only penalty that would truly hurt the North would be a cutoff of oil and other aid from China. And until now, the Chinese have feared instability and chaos in the North more than its growing nuclear and missile capability, and the Chinese leadership has refused to participate in sanctions.
Kim, believed to be about 29, appears to be betting that even a third test would not change the Chinese calculus.
It may take days or weeks to determine if the test, if that is what it proves to be, was successful. But US officials will also be looking for signs of whether the North, for the first time, conducted a test of a uranium weapon, based on an enrichment capability it has been pursuing for a decade. The past two tests used plutonium, reprocessed from one of the country’s now-defunct nuclear reactors. While the country only has enough plutonium for a half-dozen or so bombs, it can produce enriched uranium well into the future.
No country is more interested in the results of the North’s nuclear program, or the Western reaction, than Iran, which is pursuing its own uranium enrichment program. The two countries have long cooperated on missile technology, and many intelligence officials believe they share nuclear knowledge as well, though so far there is no hard evidence.
Iranians are also pursuing uranium enrichment, and one senior US official said two weeks ago that ‘‘it’s very possible that the North Koreans are testing for two countries.’’